The overall objectives of this program of research are to determine the mechanism of the neuroprotective effects of estrogens and to assess the steroid structure-neuroprotective activity relationships of the estratrienes, a group of compounds that we have discovered to be potent neuroprotectants. These objectives will be met by addressing 7 specific aims; Specific Aim 1: We will determine the role of Ca++ flux in the neuroprotective effects of estratrienes, by insulting SK-N-SH and primary cortical neuronal cultures with serum-deprivation, NMDA and beta-amyloid (Abeta) and assessing the effects of these insults and the estratrienes on intracellular Ca++ ([Ca++]). Specific Aim 2: We will determine the role of the known antioxidant effects of estratrienes in their neuroprotectivity by assessing lipid peroxidation of cell cultures in the presence and absence of the estratrienes. Specific Aim 3: We will evaluate the role of cAMP response-element binding protein (CREB) in the neurodegenerative response to insult and in the neuroprotectivity of the estratrienes. This aim will be achieved by determining the response of CREB protein and CREB gene expression to the insult and to estratrienes and by determining the effects of reductions in CREB protein, using antisense oligonucleotide transfection, on viability of cells. Specific Aim 4: in view of our observation of the phenolic A ring requirement for the neuroprotectivity of steroids against serum deprivation, we will conduct similar structure- activity evaluations to determine if a similar molecular requirement exist for the neuroprotectivity of this group of compounds against NMDA and Abeta. Specific Aims 5 and 6: We will assess the effects of th neuroprotective estratrienes in vivo to determine their effects on memory- related behavior and on basal forebrain cholinergic neurons in models of compromised cholinergic neuronal function, including ovariectomy and fimbrial lesions. Specific Aim 7: We will determine the effects of the estratrienes on memory-related behavior and cholinergic neurons in aged Fischer 344/Brown Norway F1 rats, an animal that we have shown to have a memory-related behavioral deficit. Collectively, the proposed research program represents the first systematic evaluation of an important class of compounds, some of which ar in wide use in the elderly. As such, the demonstration of the effectiveness of the estratrienes in protecting model systems from the toxicities believed to be involved in Alzheimer's disease will represent a major advancement in our ability to define a rational strategy to develop drugs to treat this devastating neurodegenerative disease.